My friends can't see me on the network.[Xonotic]

I created a game, my friends can connect the game when they are on the local network but can't see the game on the server list when they are on the different network. 
I set this to 1: sv_public= 1 
Is it an issue with my modem? How can I solve it. I would be glad if you could help. Thanks.

It might take a while for the Xonotic hub to include it. See this.
You may also need to open the port so they can connect. In some cases, you need to open the port on the modem, the router, and your local machine.